The present invention relates to a field emission element for allowing electrons to be emitted from a surface of a metal or a semiconductor by utilizing a field emission phenomenon, a method of fabricating the element, and a field emission display using the field emission element.
A field emission element, which allows electrons to be emitted from a solid due to no thermal excitation, is typically used for an electron source for drive of a FED (Field Emission Display).
As such a field emission element, there has been known a Spindt type in which a cold cathode for emitting electrons is formed into a pyramid or cone shape.
A method of fabricating the related art Spindt type field emission element will be described with reference to FIGS. 27A to 27C and FIGS. 28A and 28B.
As shown in FIG. 27A, a cathode electrode 101 made from chromium (Cr), niobium (Nb), tantalum (Ta), tungsten (W) or the like is formed into a specific pattern on a glass substrate 100. A gate electrode 103 made from Cr, Nb, Ta, W or the like is formed into a pattern crossing the pattern of the cathode electrode 101 on the cathode electrode 101 through a silicon oxide (SiO2) film 102. A resist film 104 is formed on the gate electrode 103, and an opening 105 is formed in the resist film 104 at a specific position by photolithography. Then, the gate electrode 103 is etched using the resist film 104 as an etching mask, to form an opening 106 having a diameter of about 1 xcexcm in the gate electrode 103.
As shown in FIG. 27B, the SiO2 film 102 is etched through the opening 106 of the gate electrode 103, to form a through-hole 107 in the SiO2 film 102. At this time, the SiO2 film 102 is side-etched, so that as shown in FIG. 27B, the through-hole 107 is slightly wider than the opening 106 of the gate electrode 103.
As shown in FIG. 27C, the resist film 104 is removed and a peeling layer 108 made from aluminum (Al) or the like is formed on the gate electrode 103 by oblique vapor-deposition.
As shown in FIG. 28A, a metal material such as molybdenum (Mo) or W or a semiconductor material such as diamond is vapor-deposited in the direction substantially perpendicular to the substrate 100, to form a vapor-deposition layer 109 on the gate electrode 103, and also to form, through the opening 106 of the gate electrode 103, a cathode cone (or emitter cone) 110 made from the above material on a portion of the cathode electrode 101 exposed in the through-hole 107 of the SiO2 film 102.
Then, as shown in FIG. 28B, the peeling layer 108 is removed by dissolution, to peel the vapor-deposition layer 109 on the gate electrode 103.
With these steps, a Spindt type field emission element is formed in which the cathode cone 110 as a field emission source is provided in the fine opening 106 formed in the gate electrode 103.
The field emission element thus formed is used as an electron source for drive of a display such as a FED.
For example, as shown in FIG. 29, when a specific voltage Vg is applied between the gate electrode 103 and the cathode electrode 101 of one selected from the field emission elements arranged in a matrix pattern corresponding to a matrix pattern of pixels, there occurs concentration of an electric field at a peak portion of the cathode cone 110. This allows electrons to be emitted from the peak portion of the cathode cone 110. The electrons thus emitted are accelerated by a voltage Va applied between the gate electrode 103 and a transparent electrode 111 as an anode, and then collide with a phosphor screen 112, thereby allowing light emission of the phosphor screen 112.
In the above-described related art Spindt type field emission element, field emission characteristics thereof are largely affected by a distance between the opening 106 of the gate electrode 103 and the peak portion of the cathode cone 110. On the other hand, such a distance is dependent on in-plane uniformity of thickness of the vapor-deposition film 109, and more specifically, the distance varies depending on the amplified non-uniformity of the film thickness. Accordingly, for example, in order to fabricate a display having uniform field emission characteristics, the above step of forming the vapor-deposition layer 109 is required to be carried out such that the vapor-deposition film 109 is uniformly formed at a high accuracy over the entire surface of the substrate.
However, it has been very difficult to form the vapor-deposition film 109 uniformly at a high accuracy over the entire surface of a large-area substrate, and therefore, it has failed to realize a large-area display with a high quality.
Another problem of the related art Spindt type field emission element is that the fabricating yield has been poor because of contamination of the element occurring upon peeling of the vapor-deposition layer 109.
An object of the present invention is to provide a field emission element having a structure capable of relatively easily, uniformly controlling a distance between a gate electrode and an electron emitting portion of a cathode electrode, a method of manufacturing the element, and a display using the element.
Another object of the present invention is to provide a field emission element having a structure without requiring a step of peeling a vapor-deposition layer, a method of fabricating the element, and a display using the element.
To achieve the above objects, according to a first aspect of the present invention, there is provided a field emission display having a field emission element, the field emission element including: a first electrode, and a second electrode laminated to the first electrode through an insulating layer, the first electrode having an opening, the second electrode having a hole of a planar shape corresponding to that of the opening at a position matched with the opening, the insulating layer having a through-hole continuous to the opening and the hole; wherein an upper edge portion of the hole is formed into a cross-sectional shape having an edge angle in a range of 80 to 100xc2x0; and at least part of the upper edge portion of the hole is exposed in the through-hole; whereby electrons are emitted from the second electrode through the upper edge portion of the hole exposed in the through-hole by applying a specific voltage between the first electrode and the second electrode.
According to a second aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first electrode layer on an insulating substrate; forming an insulating layer on the first electrode layer; forming a second electrode layer on the insulating layer; forming an opening in the second electrode layer at a specific position; etching the insulating layer through the opening of the second electrode layer, to form in the insulating layer a through-hole continuous to the opening of the second electrode layer and wider than the opening; and anisotropic-etching the first electrode layer through the opening of the second electrode layer and the through-hole of the insulating layer, to form in the first electrode layer a hole continuous to the through-hole of the insulating layer and having a planer shape being substantially the same as that of the opening of the second electrode layer.
According to a third aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first insulating layer on a conductive substrate or semiconductor substrate; forming a first electrode layer on the first insulating layer; forming a second insulating layer on the first electrode layer; forming a second electrode layer on the second insulating layer; forming an opening in the second electrode layer at a specific position; etching the second insulating layer through the opening of the second electrode layer, to form in the second insulating layer a through-hole continuous to the opening of the second electrode layer and wider than the opening; and anisotropic-etching the first electrode layer through the opening of the second electrode layer and the through-hole of the second insulating layer, to form in the first electrode layer a hole continuous to the through-hole of the second insulating layer and having a planar shape being substantially the same as that of the opening of the second electrode layer.
According to a fourth aspect of the present invention, there is provided a field emission display having a field emission element, the field emission element including: a first electrode, a second electrode laminated to the first electrode through a first insulating layer, and a third electrode laminated to the second electrode through a second insulating layer, the first electrode having an opening, the second electrode having a hole of a planar shape corresponding to that of the opening at a position matched with the opening, the first insulating layer having a through-hole continuous to the opening and the hole; wherein at least part of an upper edge portion of the hole is exposed in the through-hole; whereby electrons are emitted from the second electrode through the upper edge portion of the hole exposed in the through-hole by applying a first voltage between the first electrode and the second electrode and a second voltage equal to or less than the first voltage between the second electrode and the third electrode.
According to a fifth aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first electrode layer on an insulating substrate; forming a first insulating layer on the first electrode layer; forming a second electrode layer on the first insulating layer; forming a second insulating layer on the second electrode layer; forming a third electrode layer on the second insulating layer; forming an opening in the third electrode layer at a specific position; etching the second insulating layer through the opening of the third electrode layer, to form in the second insulating layer a throughhole continuous to the opening of the third electrode layer and wider than the opening; and anisotropic-etching the second electrode layer through the opening of the third electrode layer and the through-hole of the second insulating layer, to form in the second electrode layer a hole continuous to the through-hole of the second insulating layer and having a planar shape being substantially the same as that of the opening of the third electrode layer.
According to a sixth aspect of the present invention, there is provided a field emission display having a field emission element, the field emission element including: a first electrode, and a second electrode laminated on the first electrode through an insulating layer, the first electrode having an opening, the second electrode having, at a position matched with the opening, a hole having a planar shape including the opening and being partially overlapped to the opening, the insulating hole having a through-hole continuous to the opening and the hole; wherein at least part of an upper edge portion of the hole is exposed in the through-hole; whereby electrons are emitted from the second electrode through the upper edge portion of the hole exposed in the through-hole by applying a specific voltage between the first electrode and the second electrode.
According to a seventh aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first electrode layer on an insulating substrate; forming a first hole having a specific planar shape in the first electrode layer at a specific position; forming an insulating layer on the first electrode layer; forming a second electrode layer on the insulating layer; forming, in the second electrode layer at a specific position, an opening having a planar shape being partially overlapped to the first hole of the first electrode layer; etching the insulating layer through the opening of the second electrode layer, to form in the insulating layer a through-hole continuous to the opening of the second electrode layer and wider than the opening; and anisotropic-etching the first electrode layer through the opening of the second electrode layer and the through-hole of the insulating layer, to form in the first electrode layer a second hole continuous to the through-hole of the insulating layer and having a planar shape being substantially the same as that of the opening of the second electrode layer.
According to an eighth aspect of the present invention, there is provided a field emission display having a field emission element, including: a first electrode, a second electrode laminated to the first electrode through a first insulating layer, and a third electrode laminated on the second electrode through a second insulating layer, the first electrode having an opening, the second electrode having, at a position matched with the opening, a hole having a planar shape including the opening and being partially overlapped to the opening, the first insulating layer having a through-hole continuous to the opening and the hole; wherein at least part of an upper edge portion of the hole is exposed in the through-hole; whereby electrons are emitted from the second electrode through the upper edge portion of the hole exposed in the through-hole by applying a first voltage between the first electrode and the second electrode and a second voltage equal to or less than the first voltage between the second electrode and the third electrode.
According to a ninth aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first electrode layer on an insulating substrate; forming a first insulating layer on the first electrode layer; forming a second electrode layer on the first insulating layer; forming, in the second electrode layer at a specific position, a first hole having a specific planar shape; forming a second insulating layer on the second electrode layer; forming a third electrode layer on the second insulating layer; forming, in the third electrode at a specific position, a hole having a planar shape being partially overlapped to the first hole of the second electrode layer; etching the second insulating layer through the opening of the third electrode layer, to form in the second insulating layer a through-hole continuous to the opening of the third electrode layer and wider than the opening; and anisotropic-etching the second electrode layer through the opening of the third electrode layer and the through-hole of the second electrode layer, to form in the second electrode layer a second hole continuous to the through-hole of the second insulating layer and having a planar shape being substantially the same as that of the opening of the third electrode layer.
In the field emission element of the present invention, as described above, a first electrode is laminated on a second electrode through an insulating layer, and a hole having a planar shape corresponding to that of an opening provided in the first electrode is provided in the second electrode, whereby electrons are emitted from an upper edge portion of the second electrode constituting the hole.
Accordingly, a distance between the opening portion of the first electrode and the field emission portion of the second electrode can be simply, uniformly controlled only by adjustment of a thickness of the insulating layer therebetween. As a result, the field emission element of the present invention can be suitably used as an electron source for drive of a display having a large-sized screen.
In the field emission element of the present invention, since the hole of the second electrode can be formed in self-alignment to the opening of the first electrode, the fabrication method of the field emission element can be significantly simplified. Also, since there is no need of peeling of a metal vapor-deposition film as in a related art Spindt type element, it is possible to eliminate the problem of contamination of the element due to peeling of the metal vapor-deposition film, and hence to improve the fabricating yield.
According to the field emission element of the present invention, the emission efficiency of electrons from the second electrode can be improved by using as a second gate electrode a third electrode provided on the second electrode opposite to the first electrode or using as a second gate electrode a conductive substrate or semiconductor substrate provided on the second electrode opposite to the first electrode. As a result, the field emission element of the present invention can be driven at a lower voltage.